Top scientists, policy makers and industry leaders are gathering in Washington this week for a four-day symposium that will feature discussions about the past, present and future health of the ozone layer. Some key questions on the agenda: To what degree are climate change and ozone depletion interconnected? And how can leaders apply lessons learned while confronting the ozone problem that dominated headlines in the 1980s to the threats posed by global climate change? In 1987, delegates from 24 nations signed the Montreal Protocol, a landmark piece of legislation that set limits on emissions of ozone-depleting substances known as chlorofluorocarbons (CFCs). Since then, every country in the world has followed suit. The video above shows what could have happened if countries had failed to regulate CFCs. But while the Montreal Protocol began the process of closing one chapter of the ozone story, the ozone layer still requires careful monitoring because other substances in the atmosphere – including climate-altering greenhouse gases – can also affect it. In the Q & A below, NASA Goddard atmospheric scientist Paul Newman offers his perspective on why the ozone story isn’t over, and how climate change will likely impact the evolution of the ozone layer in the future. To see daily updates on the health of the ozone layer, please visit Ozone Hole Watch.

The ozone layer is on the road to recovery. Why is it still such a hot topic among scientists?It’s important to continue monitoring ozone because it’s so vital to life on Earth. Surface measurements and satellite observations confirm that ozone isn’t declining in our atmosphere anymore, so the Montreal Protocol is working. But ozone is impacted by many factors, not just CFCs. The Earth’s natural variations – like volcanic emissions, climate change, and the sun – can all impact ozone. Also, technological innovations like high-altitude aircraft or industrial chemicals can also impact it. So the ozone story isn’t over. It’s evolving.

If all of these factors influence ozone, can we say with certainty how it will change in the future?The ozone layer is recovering from the effects of CFCs, but because of climate change, it will recover to different levels than its natural pre-industrial state. Our models show that we’re not going back to the old ozone layer, we’re going back to some new version of it. Our models also show that climate has a very different impact on ozone depending on whether you’re in the troposphere or the stratosphere.

What’s the difference between the troposphere and the stratosphere?The troposphere is the lowest layer of our atmosphere, on average, extending up to about 7 miles above the Earth’s surface. Our day-to-day weather happens in the troposphere. The stratosphere extends from about 7 to 30 miles above the surface. While ozone is extremely important for screening harmful solar ultraviolet (UV) radiation, it’s a dangerous air pollutant at the Earth’s surface. Fortunately, about 90 percent of the planet’s ozone is in the stratosphere, while only 10 percent of is in the troposphere.

What about greenhouse gases? Do they also have different effects in the troposphere and stratosphere?Greenhouse gases have much different effects in the troposphere and stratosphere. Carbon dioxide both absorbs and emits infrared radiation. In the troposphere, increased levels of carbon dioxide and other greenhouse gases block outgoing radiation, increasing the surface temperature. In the stratosphere, the increasing carbon dioxide concentrations allow greater radiation to space, cooling the stratosphere. So greenhouse gases warm the surface and cool the stratosphere.

How will climate change affect ozone in the stratosphere?In the lower stratosphere, climate change will decrease the local ozone levels in the tropics and increase ozone in the mid-to-high latitudes. The “total ozone” will increase over its natural levels in the mid-latitudes in both the Northern and Southern Hemispheres – what some scientists call a “super recovery.”

How do you think the lessons learned from the ozone hole story are relevant to the climate change story?There are two important science lessons from the Montreal Protocol. The first lesson is that solid science is the foundation for policy. The quality of both ground and satellite ozone observations can now detect a 1 percent change over a 10-year period. Policy makers relied on these estimates from scientists to formulate options on the regulation of ozone depleting substances. As the science evolved, the Montreal Protocol was strengthened. The science of climate change has seen similar improvements over the last few decades. Scientists continue to improve the quality of both observations and models of climate change. The improved quality of the science allows for the formulation of effective policy.

What’s the second lesson?The Montreal Protocol demonstrates that the nations of the world can act together to solve a global problem. National boundaries are irrelevant to the stratospheric ozone layer. Emissions from countries in the Northern Hemisphere mainly caused the Antarctic ozone hole in the Southern Hemisphere. The nations of the world recognized the problem and acted together. This involved efforts between policy makers, technologists, scientists, industry, and non-governmental organizations. Technologies for replacing ozone-depleting substances have now been developed, and levels of these substances are now decreasing in our atmosphere. But we need to continue monitoring ozone and tracking how it reacts to climate gases. The story isn’t over.

My four sentence summary: Teams of researchers charged with using NPP to monitor a whole slew of environmental phenomena (think, for example, atmospheric ozone levels, sea surface temperatures, cloud properties, fire activity, vegetation cover, ocean color, land surface temperatures, aerosol particles, snow cover, the planet’s albedo, and air pollutants such as sulfur dioxide) will be doing everything they possibly can to make sure the data NPP’s instruments provide can be merged seamlessly with measurements taken by an earlier generation of satellites. Sounds easy enough, I know. It’s not. Lots and lots of careful calibration and validation work is required because four of NPP’s instruments are significantly different than the instruments that preceded them.

(Please post your guesses and your name in the comments, and we’ll give the answer next week…)

Here at What on Earth, we’re constantly stumbling across interesting photos, videos, and audio clips from NASA’s exploration of our planet (be it from space, the field, or the lab.) Whether it’s a satellite montage captured from thousands of miles up, the roar of our B-200 research aircraft, or a microscopic view of a cloud droplet, there’s literally always something strange and wonderful passing across our desks.

To have a little fun (and spare all that fascinating stuff from the circular file), we’re going to post snippets of it every now and then, usually on Fridays. What we post will change, but the question to you all will always be the same: “What on Earth is that?”

Our only hints:

Our picks will always be related to Earth science in one way or another, and…

It will have some relation to what we do at NASA.

We’ll give you a week to post your guesses, and we’ll post the answer the following Friday.

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Updated 7/16/2010

So, what on Earth was that? We received a barrage of thoughtful—and creative—responses that ranged from pollen, to DNA, to carbon nanodiamonds embedded in Antarctica ice. Ant-related answers were surprisingly common. (Nope, it isn’t an ant eating salt, spitting up acid, or laying eggs.) It is, drum roll please, a microscopic view of soot from wildfire smoke in Africa. Congratulations to posters MicroMacro (comment 121), Arbeiterkind (comment 124), Mike (comment 125), Michael & Marion Dreyer (comment 130), and Rosemary Millham (comment 141), who were correct or on the right track. A more complete description of the aerosols from this particular fire, including the image above, was published in the Journal of Geophysical Research (account required).

Here are a few more details to impress your pals: Bits

of soot (a type of aerosol particle) tend to clump together into the chain-like structures visible above. Wildfires, diesel trucks, factories—anything that partially burns the carbon locked away in fossil fuels and organic materials can produce soot and release it into the air. Soot makes doctors nervous as it can cause health problems when it lodges in our lungs and works its way into our bloodstream. And climatologists are wary of the particles as well because they absorb the sun’s energy and hasten global warming and climate change by heating the atmosphere directly or coating the surface of glaciers. In recent years, black carbon is an active area of research in climate science, and it’s a target of study for a numberof NASA’sEarth science projects, including the forthcoming Glory satellite.

Gavin Schmidt, a climatologist based at NASA’s GoddardInstitute for Space Studies (GISS) in New York City, has received the inauguralClimate Communications Prize from the American Geophysical Union, the largestassociation of Earth and planetary scientists in the world. The $25,000 prizewill be awarded at the group’s fall meeting in San Francisco thisDecember.

Here are a few links to interviews we’ve done with Schmidt in the past about communicating climate science and the surface temperature record. Also, take a look at these recent video interviews produced by Columbia and NASA and a few of Schmidt’s memorable appearances on CNN, the Daily Show, Nova, and Martha Steward (see 9:50). Congratulations, Gavin. And thank you.

The National Snow and Ice Data Center (NSIDC) has tentatively announced that Arctic sea ice has reached its minimum extent for the year. From the NSIDC release:

The blanket of sea ice that floats on the Arctic Ocean appears to have reached its lowest extent for the year. Arctic sea ice extent fell to 4.33 million square kilometers (1.67 million square miles) on September 9, 2011. This year’s minimum was the second lowest in the satellite record, which started in 1979. The lowest extent was recorded in 2007.Over the last thirty years, ice extent, a two-dimensional measure of the ice cover on the Arctic Ocean, has declined in all months, with a more pronounced drop in summer. Scientists attribute this decline in large part to climate change. Arctic sea ice melts and refreezes in an annual cycle, reaching its lowest point in late summer, and its highest point in late winter.

Meanwhile, NASA Goddard Space Flight Center has posted HD video of the decline from the near maximum ice extent in early spring of 2011 through Sept. 9, 2011. The visualization (above) is based on data collected by Aqua’sAMSR-E instrument. From Goddard’s Flickr caption:

Sea ice goes through this shrink-and-swellrhythm every year, but since consistent satellite observations began in1979, both the annual minimum at the end of summer and the annualmaximum at the end of winter continue to decline in area and thickness.Consistent with rising temperatures globally and specifically in theArctic, climate scientists are concerned with this trend both as anindicator of climate change and as a feedback mechanism. As the white,highly reflective ice disappears, darker ocean waters appear. Thisdarker surface absorbs more solar radiation and acts as a positivefeedback to the warming that is already occurring and causing the changein the first place.

Wildfires that have destroyed more than a thousand homes and threaten thousands more continue to rage in central Texas. Meteorologists point out that drought and an influx of wind from Tropical Storm Lee have fanned the flames and fueled the rash of fires, the most severe Texas has experienced in recent memory.

But what do we know about the broader context of the fires? Can we say with any certainty, for example, that fires have become more common in the United States – and across the globe – in the last few decades as global temperatures have increased?

The answer to that question, I found after hunting through various journal articles and checking in with some of Goddard Space Flight Center’s fire specialists, is complex. Satellites offer the most comprehensive and reliable measure of the amount of land burned each year; however, satellite-based records of fire activity are still relatively brief.

Still, Giglio and his colleagues have pieced together hints of trends that are worth noting. Between 1997 and 2008, they show that the number of hectares burned across the globe has declined a significant amount from a maximum in 1998 to a minimum in 2008 (see graph above). The area burned in the United States, which is less than a percent of the total area burned each year, has seen peaks in 2000 and 2007 (see graph below).

What’s driving the global decline in area burned? The topic is ripe for more research, but when I asked Giglio that question he reminded me that, contrary to what one might expect, increasing global temperatures and drought do not invariably produce increases in fire activity.

The local vegetation and climate makes a big difference, Giglio explained, noting that in certain water-limited areas, such as portions of Australia and Africa (parts of the world where the majority of burning occurs), drought can actually make wildfires less likely to occur by limiting the growth of fuel. The opposite, however, is true in places that receive moderate amounts of rain during the wet season, such as the western United States, a region for which its thought that drought will increases fire activity.

Their message: controlling black carbon emissions could be a win-win for both human health and the environment.

Not only can partially combusted particles of carbon lodge in the human respiratory system and cause disease, the panelists explained, they also contribute to climate change by warming the atmosphere and changing the way Earth reflects sunlight back into space.

Tami Bond, a black carbon specialist from the University of Illinois, began the hearing by offering a summary of black carbon’s potent short-term climate impacts. She noted, for example, that:

• One ounce of black carbon absorbs as much sunlight as would fall on an entire tennis court.

• A pound of black carbon absorbs 650 times as much energy during its one-to-two week lifetime as one pound of carbon dioxide gas would absorb during 100 years.

• An old diesel truck driving 20 miles would emit about one-third of an ounce of black carbon and 70 pounds of carbon dioxide. The carbon dioxide from that truck would have five times the warming power of the black carbon, but it would spread out over 100 years. The truck’s more potent black carbon impact would have an effect in the span of a few weeks.

Drew Shindell, a climate modeler from NASA’s Goddard Institute for Space Studies (GISS) in New York City, provided more details about where black carbon comes from and how much impact it has on Earth’s climate.

As seen in this scanning electron microscope still image, small chain-like aggregates of soot cling to larger sulfate aerosol particles. Credit: Arizona State University/Peter Buseck

Diesel vehicles, agricultural burning and wildfires, and residential cooking stoves are key sources of black carbon. However, combustion that occurs at higher temperatures — such as the type that takes place in power plants — does not produce much of the substance.

Shindell said climate models from NASA GISS and elsewhere show that 15 to 55 percent of global warming is due to black carbon. The wide range is primarily because of incomplete knowledge about how black carbon and clouds interact.

One of the more interesting questions came from Rep. Inslee, who asked the scientists whether black carbon’s impact is due to the fact that it absorbs sunlight and warms the atmosphere, or because it covers snow and ice with dark soot, which reduces Earth’s albedo and makes the planet less reflective.

Veerabhadran Ramanathan , a professor at the Scripps Institution of Oceanography, responded: “The albedo effect contributes about 10 percent of the total black carbon effect. But if you look in the Arctic or in the alpine glaciers, then the darkening effect may be the dominant effect.”

Shindell added that the scientific understanding of black carbon’s impact varies by region. “In places like the Himalayas, the results are somewhat ambiguous,” said Shindell. Over Himalayan glaciers, large amounts of dust — which also absorb radiation — and other pollutants in the air may dampen the effect. “In the Arctic, which tends to be very far from dust sources, the snow is very clean, so the effect is extremely large.” Increasing levels of black carbon combined with decreasing levels of sulfates may account for more than half of the accelerated warming in the last few decades, Shindell’s research suggests.

Inslee also expressed frustration about the lack of understanding of science and climate change among his fellow lawmakers.”If I was scientist and I knew what was going on out there, I’d be in somebody’s grill, telling them we need action,” he said. “And yet you just don’t see that from the scientific community….Why doesn’t that happen? Should it happen?”

The scientific method and the culture of scientists, Bond replied, makes it very difficult for scientists to lobby lawmakers or advocate a policy position and remain credible. “This is a difficult question and has to do with the nature of scientists and how they approach science,” she said. “If you have an action outcome, one is almost afraid that you’ll affect the science because you’re supposed to look at it dispassionately. How we conduct our business, 99.9 percent of the time, we must step back from what we want the outcome to be. We’re not allowed to want an outcome.”

As Hurricane Irene strengthens and threatens the East Coast, it seems a particularly apt time to dust off this 2007 video that explains how hot towers – immensely tall cumulonimbus clouds at the center of tropical cyclones – play a key role in strengthening storms. In 2004,researchers at Goddard Space Flight Center found that a tropical cyclone with a hot tower in its eyewall (the part of a storm the most damaging winds and rain occur) was twice as likely to intensify within the next six hours than a cyclone that lacked a tower. NASA satellites did, as detailed here, observe hot towers in Irene before forecasters elevated the storm to hurricane status.

Wandering Storms in a Warming WorldMost people know climate change is causing glaciers to retreat in Earth’s polar regions, but that’s hardly the only change warming temperatures can produce. A new study, led by Frida Bender of the Scripps Institute of Oceanography and published in Climate Dynamics, shows that the tracks of mid-latitude storms – the type that drives the weather systems that affect Americans the most – have shifted poleward and narrowed over the last 25 years as a result of climate change. What’s more, as the Jet Propulsion Laboratory’s Graeme Stephens notes in a Nature Climate Change article about the study, Bender’s satellite-based research shows that the cloudiness of the storm tracks has decreased over the same period. That’s important as it suggests the decline may have increased the net flux of radiation at the top of Earth’s atmosphere over storms – a process that could amplify warming over time.

Ocean Temperatures a Factor in Arctic Ozone LossIn March of 2011, the World Meteorological Organization put out a statement announcing an unprecedented loss of stratospheric ozone over the Arctic. Between the beginning of winter and late March ozone levels declined by 40 percent due to unusually cold temperatures in the Arctic stratosphere. (Cold temperatures hasten ozone destruction by making it possible for a certain type of cloud to form that hosts ozone-depleting chemical reactions). But what caused the cold spell? A new study authored by Margaret Hurwitz of Goddard Space Flight Center and published in Atmospheric Chemistry and Physics Discussions points out that unusually warm sea surface temperatures in the North Pacific likely played a key role. The phase of the solar cycle, greenhouse gas emissions, nor El Niño/La Niña oscillations can fully the explain the unusual conditions, she notes.

Can Satellites Help Save the Burrowing Owl?Burrowing owls, one of the world’s smallest owl species, live in the abandoned tunnels of small mammals such as ground squirrelsand prairiedogs. The long-legged birds, which typically weigh just 6 ounces, are losing ground to development and some conservation groups put the number of breeding burrowing owls at a mere 10,000. A new study, published in the Canadian Journal of Remote Sensing, suggests that crop classification imagery from Landsat satellites could be used to evaluate owl demographics and help with conservation plans as agricultural areas experience short-term changes.

Hang Tight, LandSat 5Speaking of LandSat, Landsat 5, launched in 1984, is still operating more than a quarter of a century later despite having an original design life of three years. However, the reality that LandSat 5’s critical Thematic Mapper instrument, which many agencies around the world rely upon, won’t last indefinitely is becoming increasingly difficult for scientists to ignore as the satellite ages. Since Landscape 6 failed to reach orbit and LandSat 7’s Enhanced Thematic Mapper, which reached orbit in 1999, has a glitch that omits key strips of images, there’s a real possibility that top-tier LandSat images won’t be available until the Landsat Data Continuity Mission launches in December of 2012, a new study in the Canadian Journal or Remote Sensing cautions. The Australian authors of the study tested some of the alternative satellite data products, but none of them quite measured up to LandSat 5 in their view.

Locavores Take NoteClimate models generally assume that the carbon agricultural crops take up later reenters the atmosphere in approximately the same geographic area, but in reality food gets shipped long distances before we consume it. A new paper, authored by Tristram West of the Pacific Northwest National Laboratory (PNNL) and published in Biogeosciences, accounts for the mobile nature of food and shows how regions that rely on food from distant areas end up releasing the carbon that comes with it into the atmosphere. Overall, as noted in the PNNL press release, the researchers found that crops take in — and later return — about 37 percent of the U.S.’s total annual carbon dioxide emissions, but that the amount varies significantly by region. Agriculturally active regions of the Midwest, Great Plains, and along the southern half of the Mississippi (shown in blue below) release more carbon than they take in, while more urban parts of the Northeast, Southeast, Western U.S. and Gulf Coast (shown in red below) take in more than they release.

Here at What on Earth we’re offering an extra special “no prize” if you can correctly identify the large blob-like objects and the smaller objects pointed at by the arrows.Post your guesses in the comments section, and check back next week for the answer.